The relationship between electrodiagnostic severity and
Washington Neuropathic Pain Scale in patients
with carpal tunnel syndrome
Karpal tünel sendromlu hastalarda elektrodiyagnostik tanı ile
Washington Nöropatik Ağrı Ölçeği arasındaki ilişki
Çağatay ÖNCEL,1 L. Sinan BİR,1 Engin SANAL2
Summary
Objectives: We undertook this study to examine the relationships between clinical symptoms as evaluated by Washington
Neuropathic Pain Scale (NPS) and electrodiagnostic classifi cation in patients with carpal tunnel syndrome (CTS).
Methods: Eighty patients with unilateral CTS were included in this study. After diagnosis of CTS by electromyography, all
patients completed a 10-item questionnaire (NPS).
Results: A statistically signifi cant correlation between total NPS score and severity of CTS was found (p=0.013, r=0.276). Conclusion: Th e present study indicates that using NPS might be useful in evaluating the clinical outcome of patients with CTS.
Key words: Carpal tunnel syndrome; neuropathic pain scale.
Özet
Amaç: Karpal tünel sendromu (KTS) olan hastaların, Washington Nöropatik Ağrı Ölçeği (NAÖ) ile değerlendirdiğimiz klinik
semptomları ile elektrodiyagnostik sınıfl amaları arasındaki ilişki olup olmadığını saptamayı amaçladık.
Gereç ve Yöntem: Tek tarafl ı KTS’si olan seksen hasta çalışmaya alındı. Elektromiyografi k olarak KTS tanısı konduktan sonra,
hastalar 10 soru içeren NAÖ’yü yanıtladılar.
Bulgular: NAÖ’nün toplam değeriyle KTS’nin şiddeti arasında istatiksel olarak anlamlı bir korelasyon bulundu (p=0.013,
r=0.276).
Sonuç: Çalışmamızda, NAÖ’nün KTS’li hastaların klinik gidişini değerlendirmede yararlı olduğu sonucuna varıldı. Anahtar sözcükler: Karpal tünel sendromu; nöropatik ağrı ölçeği.
Departments of 1Neurology and 2Physical Medicine and Rehabilitation, Pamukkale University, Faculty of Medicine, Denizli, Turkey
Pamukkale Üniversitesi Tıp Fakültesi, 1Nöroloji Anabilim Dalı, 2Fizik Tedavi ve Rehabilitasyon Anabilim Dalı, Denizli
Submitted - February 20, 2009 (Başvuru tarihi - 20 Şubat 2009) Accepted after revision - July 25, 2009 (Düzeltme sonrası kabul tarihi - 25 Temmuz 2009)
Correspondence (İletişim): Çağatay Öncel, M.D. Hastane Cad., Saraylar Mah., No: 26, Kat: 1, Denizli, Turkey. Tel: +90 - 258 - 444 07 28 / 2138 Fax (Faks): +90 - 258 - 242 35 12 e-mail (e-posta): cagatay_oncel@yahoo.com
AĞRI 2009;21(4):146-148 CLINICAL TRIALS - KLİNİK ÇALIŞMA
EKİM - OCTOBER 2009 146
EKİM - OCTOBER 2009 147
Introduction
Carpal tunnel syndrome (CTS) is an entrapment neuropathy of the median nerve at the wrist. Diag-nosis of CTS is based on clinical symptoms,
physi-cal signs and nerve conduction abnormalities. Th e
classic symptoms of CTS are numbness and pares-thesia in the fi rst three fi ngers of the hand, which is
exacerbated at night. Th e diagnostic signs include
sensory loss along the lateral aspect of the hand, mo-tor weakness and wasting of the abducmo-tor pollicis brevis muscle. Additional tests have been described to obtain the correct diagnosis, including Phalen’s test and Tinel’s sign. Nerve conduction studies and electromyography have also been employed for many years. Although the electrophysiological test-ing is accepted as a standard for diagnosis of CTS, no tool quantifying the severity of symptoms has been standardized thus far. Assessment of the sever-ity and qualsever-ity of the symptoms is useful in
evaluat-ing the outcome of the treatment.[1-3]
Th e Washington Neuropathic Pain Scale (NPS) was
created in recent years to evaluate neuropathic pain and is composed of 10 units. In this study, we inves-tigated the correlation between the clinical symp-tom results of patients according to NPS and elec-trodiagnostic classifi cation.
Materials and Methods
Eighty patients with unilateral CTS were included
in this prospective study. Th e study was approved
by the Institutional Review Board at our institution. An electromyography and nerve conduction veloc-ity system (Medelec Premiere Plus, UK) was used in
the present study. Th e standard motor and sensory
nerve conduction study of median and ulnar nerves
was performed in both hands in all patients. Th e
temperature was maintained at >32 ºC during the procedure. CTS was defi ned as present when ulnar nerve studies were normal and median nerve stud-ies met one of the following criteria for abnormality based on normal values obtained and used in our laboratory: Distal peak latency of sensory nerve ac-tion potential (DL-S) >3.8 ms, distal onset latency of compound muscle action potential (DL-M) >4.4 ms, and conduction velocity of sensory nerve fi bers (CV-S) <50 m/s.
Patients diagnosed with CTS were classifi ed
accord-ing to the severity of CTS. Th e American
Associa-tion of Electrodiagnostic Medicine criteria[4] was
used for detection of severity of CTS. Th e criteria
are as follows:
Mild CTS- Prolonged (relative or absolute) sensory or mixed nerve action potential (NAP) distal laten-cy (orthodromic, antidromic or palmar) ± sensory nerve action potential (SNAP) amplitude below the lower limit of normal;
Moderate CTS- Abnormal median sensory latencies as above and (relative or absolute) prolongation of median motor distal motor latency;
Severe CTS- Prolonged median motor and sensory distal motor latencies, with either an absent SNAP or mixed NAP, or low amplitude or absent thenar muscle action potential.
After diagnosis of unilateral CTS, patients gave in-formed consent and immediately completed a
10-item questionnnaire (NPS). Th e NPS presents 10
domains of pain including two items that assess global pain intensity and pain unpleasantness and eight items that assess the locations of neuropathic pain and specifi c qualities as: sharp, hot, dull, hot, cold, sensitive, itchy, and deep or surface.[5] Subjects
were asked to rate each quality of pain on a scale of 0 to 10, with 0= no pain and 10= the most sensation imaginable. We then investigated whether there was any correlation between classifi cation of CTS and the NPS scale.
SPSS (SPSS for Windows version 13.0) was used for statistical analysis. Pearson’s correlation analysis was used to assess the relationships between the NPS score and electrodiagnostic classifi cation. Signifi -cance levels were set at p<0.05 in all cases.
Results
Eighty patients participated in this study,
yield-ing 80 hands with CTS. Th ere were 17 men and
63 women (1/3.7). Th e mean age of patients was
46.7±12.6 years (range: 23-80). Th e mean NPS
score was 37.5±12.3 (11-68). Forty-six hands (57.5%) were categorized as mild CTS, 29 (36.3%) as moderate CTS and 5 (6.2%) as severe CTS. Forty-fi ve (56.2%) right and 35 (43.8%) left hands The relationship between electrodiagnostic severity and NPS in patients with carpal tunnel syndrome
AĞRI
EKİM - OCTOBER 2009 148
were involved. Right or left hand involvement was not related to the severity of the clinical involvement (p=0.76). Duration of the symptoms was 7.4±4.3 months.
A statistically signifi cant correlation between total NPS score and severity of CTS was found (p=0.013, r=0.276). In addition, there was a statistically sig-nifi cant correlation between the severity of CTS and the four parameters of NPS (intensity, hot,
un-pleasantness, deep). Th e correlation coeffi cients are
shown in Table 1.
Discussion
A correlation was found between the total NPS score, the intensity, hot, unpleasantness, and deep pain parameters and severity of electrodiagnostic
CTS. Th is correlation shows that there is a
relation-ship between some clinical symptoms and sever-ity of electrodiagnostic CTS. 91-98% of the clini-cally diagnosed cases demonstrate abnormality on
electrodiagnostic studies.[6] However, the patient
sometimes has no symptoms despite the presence of severe electrodiagnostic fi ndings. In exact contradic-tion, severe symptoms may exist despite very mild electrodiagnostic fi ndings. While some studies have described a relation between clinical symptoms and
severity of electrodiagnosed CTS, others did not.[7-9]
Th ere are studies in the literature that have
evalu-ated the relationship between the symptom
sever-ity scales and seversever-ity of electrodiagnosed CTS.[10,11]
You et al.[10] found a correlation between
electrodi-agnostic fi ndings and symptom severity scale. Th is
scale consisted of questions about pain, weakness, clumsiness, numbness, and tingling. On the other
hand, Levine et al.[11] was unable to show any
rela-tion between the symptom severity scale and elec-trodiagnostic fi ndings. However, they did not exam-ine relationships between subgroups of symptoms and electrodiagnostic measures.
However, there has been no study that evaluates this relationship according to NPS, which is practical
and easy to apply. Th e NPS is painless and easy to
administer virtually everywhere. Th e present study
indicates application of the NPS scale might be use-ful in evaluating the clinical outcome of patients with CTS.
References
1. Kamath V, Stothard J. A clinical questionnaire for the diagnosis of carpal tunnel syndrome. J Hand Surg Br 2003;28(5):455-9. 2. Padua L, Padua R, LoMonaco M, Romanini E, Tonali P. Italian
multicentre study of carpal tunnel syndrome: study design. Italian CTS Study Group. Ital J Neurol Sci 1998;19(5):285-9. 3. Padua L, LoMonaco M, Gregori B, Valente EM, Padua R,
To-nali P. Neurophysiological classifi cation and sensitivity in 500 carpal tunnel syndrome hands. Acta Neurol Scand 1997;96(4):211-7.
4. Stevens JC. AAEM minimonograph: the electrodiagnosis of carpal tunnel syndrome. American Association of Electrodi-agnostic Medicine. Muscle Nerve 1997;20(12):1477-86. 5. Galer BS, Jensen MP. Development and preliminary
valida-tion of a pain measure specifi c to neuropathic pain: the Neu-ropathic Pain Scale. Neurology 1997;48(2):332-8.
6. Oh SJ. Nerve conductions in focal neuropathies. In: Retford DC, editor. Clinical electromyography: Nerve Conduction Studies. 2nd ed. Baltimore: Williams & Wilkins; 1993. p. 496-574. 7. Bland JD. A neurophysiological grading scale for carpal
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8. Padua L, Padua R, Lo Monaco M, Aprile I, Tonali P. Mul-tiperspective assessment of carpal tunnel syndrome: a multicenter study. Italian CTS Study Group. Neurology 1999;53(8):1654-9.
9. de Campos CC, Manzano GM, Leopoldino JF, Nóbrega JA, Sa-ñudo A, de Araujo Peres C, et al. The relationship between symptoms and electrophysiological detected compres-sion of the median nerve at the wrist. Acta Neurol Scand 2004;110(6):398-402.
10. You H, Simmons Z, Freivalds A, Kothari MJ, Naidu SH. Re-lationships between clinical symptom severity scales and nerve conduction measures in carpal tunnel syndrome. Muscle Nerve 1999;22(4):497-501.
11. Levine DW, Simmons BP, Koris MJ, Daltroy LH, Hohl GG, Fos-sel AH, et al. A Fos-self-administered questionnaire for the assess-ment of severity of symptoms and functional status in carpal tunnel syndrome. J Bone Joint Surg [Am] 1993;75(11):1585-92.
Table 1. Pearson correlation coeffi cients for NPS parameters of CTS
NPS parameters CTS severity p-Value R
Intensity 0.001 0.359 Sharp 0.179 0.153 Dull 0.145 0.164 Hot 0.005 0.31 Cold 0.236 0.134 Sensitive 0.139 0.168 Itchy 0.203 0.144 Unpleasantness 0.002 0.346 Deep 0.04 0.23 Surface 0.98 0.003 Total score 0.013 0.276
